<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>边框</title>
    <style>
        div {
            width: 300px;
            height: 200px;
            /* border-width: 5px;边框粗细   为5px */
            border-width: 5px;
            /* border-style: solid;边框样式  实线  虚线dashed   点线dotted */
            border-style: solid;
             /* 边框颜色 */
            background-color: rgb(221, 207, 207);
            /* 边框复合写法  简写 */
            border: 12px solid red ;
            /* 边框为蓝色 */
            border-bottom:12px solid rgba(101, 7, 253, 0.918);
            /* 上边框为红色  层叠上边框  */
            border-top: 12px solid rgb(24, 8, 8);
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>